Block-oriented Magnetic Tape Drives

Probably the "big daddy" of all of the block-addressable tape systems would be the Control Data SCROLL device. Never made it to production and mentioned here only: http://special.lib.umn.edu/findaid/xml/cbi00080-07.xml There might be other mentions in publications of the time (ca. 1971-75); I know that it was attached as boilerplate for several proposals that I worked on. Basically, a very wide tape, where between the supply and takeup spools was positioned a head-per-track spinning drum, with the tape being wrapped, VHS-style, around the drum. The block accessed by the head could be accessed by simply moving the tape under the heads. Another one of those whacky ADL projects, I never saw an operating one, but doubtless there are patents on it. Maybe CHM has some documents on it--and the STAR Drum, a freaky ultra-high-speed drum spinning on magnetic bearings in vacuo. Were the tapes used in the IBM 3850 block-addressable? --Chuck